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SubjectRe: [PATCH v3 1/4] wait.[ch]: Introduce the simple waitqueue (swait) implementation
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On 11/04/2015 11:33 AM, Thomas Gleixner wrote:
> On Tue, 20 Oct 2015, Daniel Wagner wrote:
>> +
>> +extern void swake_up(struct swait_queue_head *q);
>> +extern void swake_up_all(struct swait_queue_head *q);
>> +extern void swake_up_locked(struct swait_queue_head *q);
>
> I intentionally named these functions swait_wake* in my initial
> implementation for two reasons:
>
> - typoing wake_up vs. swake_up only emits a compiler warning and does
> not break the build

I played a bit around on this and came up with the patch below. The type
check results in an error.

> - I really prefer new infrastructure to have a consistent prefix
> which reflects the "subsystem". That's simpler to read and simpler
> to grep for.
>
>> +extern void __prepare_to_swait(struct swait_queue_head *q, struct swait_queue *wait);
>> +extern void prepare_to_swait(struct swait_queue_head *q, struct swait_queue *wait, int state);
>> +extern long prepare_to_swait_event(struct swait_queue_head *q, struct swait_queue *wait, int state);
>> +
>> +extern void __finish_swait(struct swait_queue_head *q, struct swait_queue *wait);
>> +extern void finish_swait(struct swait_queue_head *q, struct swait_queue *wait);
>
> Can we please go with the original names?
>
> swait_prepare()
> swait_prepare_locked()
> swait_finish()
> swait_finish_locked()
>
> Hmm?

I defer to Peter :)

>> +#define swait_event(wq, condition) \
>
> Here we have the same swait vs. wait problem as above. So either we
> come up with a slightly different name or have an explicit type check
> in __swait_event event.

What about something like this:

diff --git a/include/linux/swait.h b/include/linux/swait.h
index c1f9c62..f59369d 100644
--- a/include/linux/swait.h
+++ b/include/linux/swait.h
@@ -6,6 +6,9 @@
#include <linux/spinlock.h>
#include <asm/current.h>

+#define compiletime_assert_same_type(a, b) \
+ compiletime_assert(__same_type(a, b), "Need to match correct type");
+
/*
* Simple wait queues
*
@@ -66,6 +69,7 @@ extern void __init_swait_queue_head(struct swait_queue_head *q, const char *name
#define init_swait_queue_head(q) \
do { \
static struct lock_class_key __key; \
+ compiletime_assert_same_type(struct swait_queue_head *, q); \
__init_swait_queue_head((q), #q, &__key); \
} while (0)



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